#define _CRT_SECURE_NO_WARNINGS 1
#include <iostream>
#include <vector>
using namespace std;

int main() {
    int n = 0;
    cin >> n;
    vector<int> cost(n);
    for (int i = 0;i < n;i++)
    {
        cin >> cost[i];
    }
    vector<int> dp(n + 1);
    for (int i = 2;i < n + 1;i++)
    {
        dp[i] = min(dp[i - 1] + cost[i - 1], dp[i - 2] + cost[i - 2]);
    }
    cout << dp[n] << endl;
    return 0;
}